A silicon wafer has been widely used as a substrate of a semiconductor device. In a semiconductor device, the metal contamination of a substrate leads to reduction of the device performances. This entails a demand for a silicon wafer with less metal contamination. In order to provide a silicon wafer with less metal contamination, it is desirable to analyze the metal contamination of a silicon wafer, to perform quality determination based on the analysis results, and to perform a treatment for reducing the metal contamination in the silicon wafer manufacturing steps based on the analysis results, if required.
The analysis of the metal contamination of a silicon wafer can be performed by, for example, decomposing (etching) the silicon wafer surface layer region and analyzing the metal components in the decomposed residues. Examples of known decomposing methods include a method including bringing the silicon wafer surface into contact with a decomposing solution to dissolve and decompose the silicon wafer surface (liquid phase decomposition), and a method including bringing the silicon wafer surface to be decomposed into contact with etching gas to decompose the silicon wafer surface (vapor phase decomposition) (see, e.g., Japanese Patent Application Publication No. 2008-130696, which is expressly incorporated herein by reference in its entirety).